Re: current state of USB SUSPEND?

On Wed, 18 Apr 2007, Jiri Kosina wrote:

> On Wed, 18 Apr 2007, Jeroen Janssen wrote:
> 
> > I noticed several recent USB SUSPEND related patches on this mailinglist 
> > and I was wondering if someone could tell me what the current state of 
> > USB SUSPEND is. Should USB devices be suspend 'automaticly' (by the 
> > kernel) when suspending to ram? Or do I need to manually suspend the 
> > devices somehow?
> 
> Hi Jerome,
> 
> USB suspend is not closely related to suspending of the system 
> (swsusp/acpi). USB suspend is independent, and allows for USB-specific 
> suspending of devices that have not been recently used, to reduce power 
> consumption. The USB_SUSPEND feature has been present in mainline kernel 
> for quite some time, under CONFIG_USB_SUSPEND option.
> 
> The patches that have been discussed lately here were related to some 
> changes of the usb suspend architecture, allowing per-device specification 
> of timeout before putting device to suspend, etc.

And to answer Jeroen's question: Yes, USB devices should be suspended
automatically by the kernel when you suspend-to-ram.  You don't need to do 
anything manually to suspend them.

Alan Stern


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